The present invention is directed to a method and circuit arrangement for the redirection of a message cell stream from an active route onto an alternative route within a cell-oriented communication network.
Such a method and such a circuit arrangement are already known from Ohta, H., Ueda, H., "Hitless Line Protection Switching Method for ATM Networks", IEEE International Conference on Communications ICC '93, pp. 272-276. Given this known method or, respectively, given this known circuit arrangement, a separate control means is respectively provided at the output of a switching equipment located at the start of a line pair and is also provided at the input of a switching equipment located at the end of the line pair. A message cell stream to be transmitted is thereby duplicated by the control means located at the appertaining output in order to transmit two identical message cell streams over the line pair to the control means that is located at the end of the line pair. The latter effects a synchronization of the two supplied message cell streams as well as a forwarding of the message cell stream transmitted over the line of the line pair defined as alternate line after the synchronization has been carried out. Three different methods are disclosed for this. Specific control cells are employed in two of these methods, whereas the remaining method is a bit-by-bit comparison of the message cells transmitted over the line pair.
Given the known method or, respectively, given the known circuit arrangement, an interruption-free alternate routing of the entire line capacity is only possible between the two lines belonging to the line pair. No subcapacities, for example in the form of individual, virtual path connections, can be redirected between the two lines. Over and above this, a separate decentralized control means is required at the output side per line pair, so that a high circuit-oriented outlay is necessary when a plurality of line pairs proceeds between switching equipment connected to one another.